Related

The Supreme Court agreed Tuesday to decide whether to block key aspects of the Obama administration's plan aimed at cutting power plant and factory emissions of gases blamed for global warming.

The justices said they will review a unanimous federal appeals court ruling that upheld the government's unprecedented regulation of carbon dioxide and five other heat-trapping gases.

The question in the case is whether the Environmental Protection Agency's authority to regulate automobile emissions of greenhouses gases as air pollutants, which stemmed from a 2007 Supreme Court ruling, also applies to power plants and factories.

The court's decision essentially puts on trial a small but critical piece of President Barack Obama's toolbox to tackle global warming -- a requirement that companies expanding existing industrial facilities or building new ones that would increase overall pollution must evaluate ways to reduce the carbon they release, as well. For many industrial facilities, this is the only way heat-trapping gases will be regulated, until the EPA sets national standards.

That's because the administration's plans hinge on the high court's 2007 ruling in Massachusetts v. EPA which said the EPA has the authority, under the Clean Air Act, to limit emissions of greenhouse gases from vehicles. Two years later, Obama's EPA concluded that the release of carbon dioxide and other heat-trapping gases endangered human health and welfare, a finding the administration has used to extend its authority beyond automobiles to develop national standards for large stationary sources.

The administration currently is at work setting first-time national standards for new and existing power plants, and will move on to other large stationary sources. But in the meantime, the only way companies are addressing global warming pollution is through a permitting program that requires them to analyze the best available technologies to reduce carbon dioxide, the chief greenhouse gas.

The president gave the EPA until next summer to propose regulations for existing power plants, the largest unregulated source of global warming pollution.

EPA Administrator Gina McCarthy said the court will take up "a very narrow legal question" and otherwise confirmed "that EPA has the authority to protect public health by reducing carbon pollution under the Clean Air Act."

Michael Gerrard, a law professor at Columbia University and director of its Center for Climate Change Law, saw it somewhat differently. "From an environmental standpoint, it is bad, but not catastrophic," Gerrard said. He added that it would have been far worse if the court decided to question the EPA's conclusion that greenhouse gases endanger human health and welfare.

Environmental groups generally breathed a sigh of relief that the court rejected calls to overrule its 2007 decision or review the EPA's conclusion about the health effects of greenhouse gas emissions.

"It's a green light for EPA to go ahead with its carbon pollution standards for power plants because the court has left standing EPA's endangerment finding," said Joanne Spalding, the Sierra Club's senior managing attorney.

But a lawyer for some of the business groups involved in the case said the court issued a more sweeping ruling.

"Read in its broadest sense, it arguably opens the door to whether EPA can regulate greenhouse gases from stationary sources at all," said Roger Martella, a partner with the Sidley, Austin law firm in Washington.

The regulations have been in the works since 2011 and stem from the landmark Clean Air Act that was passed by Congress and signed by President Richard Nixon in 1970 to control air pollution.

The administration has come under fierce criticism from Republicans for pushing ahead with the regulations after Congress failed to pass climate legislation, and after the administration of President George W. Bush resisted such steps.

In 2012, a three-judge panel of the U.S. Court of Appeals for the District of Columbia Circuit concluded that the EPA was "unambiguously correct" in using existing federal law to address global warming.

The judges on that panel were: then-Chief Judge David Sentelle, who was appointed by Republican President Ronald Reagan, and David Tatel and Judith Rogers, both appointed by Democrat Bill Clinton.